She isn't a Vocaloid anymore, yes, she *was* but she isn't now.
She left the Vocaloid engine.
Miku was never the best vocal, but she had English, Japanese, Chinese, several alternative voicebanks and she was better then most overall because of what she offered. However, her main vocal, didn't do everything and there just were better vocals then it.
Fans often think their favourite Vocaloid is the best and have trouble accepting it may not. their bias towards it because they like how it sounds,they don't know how good or bad it actually is unless they speak Japanese and know how to make music, use vocaloid.